I would like to offer some improvements to the TreeStore and loading issues. Already in the ExtJS 3, I noticed that the TreeLoader expects the json structure of pure node array only. No additional information like success indicator or a warning message or an error message could be sent as response.

In ExtJS 3, I solved this problem by putting this information in the first reserved node and made it invisible.

Since in the ExtJS 4, the tree is a table and the tree store is a store, it would make sense to make the expected json structure for the tree store like it is for the normal store - not just pure array of nodes but

- the base response object where the success indicator, error messages etc could be put
- the 'root' property where the record collection is found

The 'root' property could be then specified like by normal Stores in the reader. I will override the TreeStore and related classes for my solution, but I think it make sense to make this general and universal approach which is used for the normal Stores also for the TreeStore.